This research investigates respiratory control in both normal subjects and in patients with respiratory system abnormalities by examining aspects of respiratory muscle function under various states and with several respiratory stimuli. In the first of three phases of the study the segmental muscle reflexes are examined using the electromyographic responses of the important respiratory muscles to sudden respiratory loads (airway resistance or occlusion) and to the release of resistive loads. In the second phase of the study, the integrated electromyograms (EMG's) of various respiratory muscles, including surface recordings from the diaphragm, several intercostals, the scaleni and the sternocleidomastoids, will be evaluated as measures respiratory control system output by comparison to ventilatory responses, airway occlusion pressures (PO.1) and the diaphragmatic EMG via esophageal electrodes, during standardized tests of responses to hypercapnia, hypoxia and exercise. The third phase of the study combines the techniques of sleep research and respiratory physiology to investigate the relationships between the states of sleep (quiet vs R.E.M.) and respiratory control. Using both EMG's of respiratory muscles and magnetometer measurements of thoraco-abdominal motion, patterns of breathing, reflex responses to loading and responses to hypercapnia will be assessed in both normals and respiratory disease patients while awake and in both quiet and R.E.M. sleep.